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1 | |
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2 | adns |
3 | |
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4 | Advanced, easy to use, asynchronous-capable DNS client library. |
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5 | |
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6 | adns is a resolver library for C (and C++) programs. In contrast with |
7 | the existing interfaces, gethostbyname et al and libresolv, it has the |
8 | following features: |
9 | * It is reasonably easy to use for simple programs which just want |
10 | to translate names to addresses, look up MX records, etc. |
11 | * It can be used in an asynchronous, non-blocking, manner. Many |
12 | queries can be handled simultaneously. |
13 | * Responses are decoded automatically into a natural representation |
14 | for a C program - there is no need to deal with DNS packet |
15 | formats. |
16 | * Sanity checking (eg, name syntax checking, reverse/forward |
17 | correspondence, CNAME pointing to CNAME) is performed |
18 | automatically. |
19 | * Time-to-live, CNAME and other similar information is returned in |
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20 | an easy-to-use form, without getting in the way. |
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21 | * There is no global state in the library; resolver state is an |
22 | opaque data structure which the client creates explicitly. A |
23 | program can have several instances of the resolver. |
24 | * Errors are reported to the application in a way that distinguishes |
25 | the various causes of failure properly. |
26 | * Understands conventional resolv.conf, but this can overridden by |
27 | environment variables. |
28 | * Flexibility. For example, the application can tell adns to: ignore |
29 | environment variables (for setuid programs), disable sanity checks |
30 | eg to return arbitrary data, override or ignore resolv.conf in |
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31 | favour of supplied configuration, etc. |
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32 | * Believed to be correct ! For example, will correctly back off to |
33 | TCP in case of long replies or queries, or to other nameservers if |
34 | several are available. It has sensible handling of bad responses |
35 | etc. |
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36 | |
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37 | Forthcoming: |
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38 | |
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39 | I hope that future versions may also have the following features: |
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40 | * The library will be useable by threads in a multithreaded program |
41 | in a natural way. It will multiplex many threads' queries through |
42 | a single query socket. |
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43 | * Limited caching behaviour. |
44 | * IPv6 support. |
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45 | |
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46 | (Technical note: adns requires a real nameserver like BIND running on |
47 | the same system or a nearby one, which must be willing to provide |
48 | `recursive service'. I.e., adns is a `stub resolver'. All properly |
49 | configured UN*X and GNU systems will already have such nameserver(s); |
50 | they are usually listed in /etc/resolv.conf.) |
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51 | |
52 | Feedback |
53 | |
54 | If you are subscribed to adns-discuss please send bug reports there; |
55 | otherwise mail them to adns-bugreports@chiark.greenend.org.uk. |
56 | |
57 | Mailinglists |
58 | |
59 | I have set up mailinglists adns-announce and adns-discuss. The |
60 | announcements list is moderated and will contain only announcements of |
61 | important bugs, new versions, &c. The bug reports address mentioned |
62 | above is also a mailing list; feel free to subscribe to it. |
63 | |
64 | There are [1]archives and subscription web pages, or you can subscribe |
65 | by sending mail containing the word `subscribe' to |
66 | adns-announce-REQUEST@chiark.greenend.org.uk or |
67 | adns-discuss-REQUEST@chiark.greenend.org.uk. |
68 | |
69 | Download |
70 | |
71 | Available for download from [2]chiark.greenend.org.uk are: |
72 | * The [3]current pre-release version as a gzipped tarfile. |
73 | * All released versions are also available via [4]anonymous FTP. |
74 | |
75 | adns is also available from the GNU Project FTP servers and their |
76 | mirrors. |
77 | |
78 | Copyright and licensing |
79 | |
80 | adns is Copyright 1997-1999 Ian Jackson. |
81 | |
82 | adns is free software; you can redistribute it and/or modify it under |
83 | the terms of the GNU General Public License as published by the Free |
84 | Software Foundation; either version 2 of the License, or (at your |
85 | option) any later version. |
86 | |
87 | This program and documentation is distributed in the hope that it will |
88 | be useful, but without any warranty; without even the implied warranty |
89 | of merchantability or fitness for a particular purpose. See the [5]GNU |
90 | General Public License for more details. |
91 | |
92 | You should have received a copy of the GNU General Public License |
93 | along with adns, or one should be available above; if not, write to |
94 | the [6]Free Software Foundation, 59 Temple Place - Suite 330, Boston, |
95 | MA 02111-1307, USA, or email adns-maint@chiark.greenend.org.uk. |
96 | _________________________________________________________________ |
97 | |
98 | [7]Ian Jackson / [8]adns-maint@chiark.greenend.org.uk; more [9]free |
99 | software by me. |
100 | |
101 | [10]GNU home page; [11]site or mirror home page |
102 | |
103 | This web page is Copyright (C)1996-1999 Ian Jackson. See the |
104 | [12]Copyright/acknowledgements. |
105 | |
106 | Use any browser - [13]Campaign for a non-browser-specific WWW |
107 | |
108 | References |
109 | |
110 | 1. http://www.chiark.greenend.org.uk/mailman/listinfo |
111 | 2. http://www.chiark.greenend.org.uk/ |
112 | 3. http://www.chiark.greenend.org.uk/~ian/adns/adns.tar.gz |
113 | 4. ftp://ftp.chiark.greenend.org.uk/users/ian/userv/ |
114 | 5. http://www.chiark.greenend.org.uk/~ian/COPYING.txt |
115 | 6. http://www.fsf.org/ |
116 | 7. http://www.chiark.greenend.org.uk/ |
117 | 8. mailto:adns-maint@chiark.greenend.org.uk |
118 | 9. http://www.chiark.greenend.org.uk/~ian/software/ |
119 | 10. http://www.gnu.org/ |
120 | 11. http://www.chiark.greenend.org.uk/ |
121 | 12. http://www.chiark.greenend.org.uk/~ian/sw-www-copy.html |
122 | 13. http://www.anybrowser.org/campaign/ |